com.bigdata.counters.CAT Maven / Gradle / Ivy
/**
Copyright (C) SYSTAP, LLC DBA Blazegraph 2006-2016. All rights reserved.
Contact:
SYSTAP, LLC DBA Blazegraph
2501 Calvert ST NW #106
Washington, DC 20008
[email protected]
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
/*
* Created on May 11, 2010
*/
package com.bigdata.counters;
import java.io.Externalizable;
import java.io.IOException;
import java.io.ObjectInput;
import java.io.ObjectOutput;
import java.util.concurrent.atomic.AtomicLong;
import org.cliffc.high_scale_lib.ConcurrentAutoTable;
/**
* An alias for the high-scale-lib counter implementation. {@link CAT}s are
* useful when a counter is extremely hot for updates and adaptively expand
* their internal state to minimize thread contention. However, they can do more
* work than an {@link AtomicLong} on read since they must scan an internal
* table to aggregate updates from various threads.
*
* Note: The class uses a delegation pattern in order to replace the
* serialization logic with a simple serialized long value.
*
* @see ConcurrentAutoTable
*
* @author Bryan Thompson
* @version $Id$
*/
public class CAT /*extends ConcurrentAutoTable*/ implements Externalizable {
/**
*
*/
private static final long serialVersionUID = 1L;
private ConcurrentAutoTable cat;
/**
* Initialize a new counter with a value of 0L.
*/
public CAT() {
cat = new ConcurrentAutoTable();
}
/**
* Add the value to the counter.
*
* @see ConcurrentAutoTable#add(long)
*/
final public void add(long x) {
cat.add(x);
}
/** Decrement the value of the counter.
*
* @see ConcurrentAutoTable#decrement()
*/
final public void decrement() {
cat.decrement();
}
/**
* Increment the value of the counter.
*
* @see ConcurrentAutoTable#increment()
*/
final public void increment() {
cat.increment();
}
/**
* Set the value of the counter.
*
* @see ConcurrentAutoTable#set(long)
*/
final public void set(long x) {
cat.set(x);
}
/**
* Current value of the counter.
*
* @see ConcurrentAutoTable#get()
*/
final public long get() {
return cat.get();
}
/**
* Estimate the current value of the counter.
*
* @see ConcurrentAutoTable#estimate_get()
*/
final public long estimate_get() {
return cat.estimate_get();
}
@Override
public void writeExternal(ObjectOutput out) throws IOException {
out.writeLong(get());
}
@Override
public void readExternal(ObjectInput in) throws IOException,
ClassNotFoundException {
cat.set(in.readLong());
}
/**
* Return the current value of the counter.
*/
@Override
public String toString() {
return Long.toString(cat.get());
}
}